PTHH: \(2K+2H_2O\rightarrow2KOH+H_2\)
Ta có: \(n_K=\frac{7,8}{39}=0,2\left(mol\right)\)
\(\Rightarrow\left\{{}\begin{matrix}n_{H_2}=0,1mol\\n_{KOH}=0,2mol\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}V_{H_2}=0,1\cdot22,4=2,24\left(l\right)\\m_{KOH}=0,2\cdot56=11,2\left(g\right)\end{matrix}\right.\)